carols10cents commented on code in PR #15030:
URL: https://github.com/apache/datafusion/pull/15030#discussion_r1985207813
##########
datafusion/physical-plan/src/execution_plan.rs:
##########
@@ -260,13 +260,30 @@ pub trait ExecutionPlan: Debug + DisplayAs + Send + Sync {
/// used.
/// Thus, [`spawn`] is disallowed, and instead use [`SpawnedTask`].
///
+ /// To enable timely cancellation, the [`Stream`] that is returned must not
+ /// pin the CPU and must yield back to the tokio runtime regularly. This
can
+ /// be achieved by manually returning [`Poll::Pending`] in regular
intervals,
+ /// or the use of [`tokio::task::yield_now()`]. Cooperative scheduling may
also
+ /// be a way to achieve this goal, as [tokio support for it
improves][coop].
+ /// Determination for "regularly" may be made using a timer (being careful
with
+ /// the overhead-heavy syscall needed to take the time) or by counting
rows or
+ /// batches.
+ ///
+ /// The goal is for `datafusion`-provided operator implementation to
+ /// strive for [the guideline of not spending a long time without reaching
Review Comment:
Could someone make a concrete suggestion here on how the text should be
changed for discussion?
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